17th Philippine Chemistry Congress
May 23-25, 2001
Cagayan de Oro CityABSTRACTS: POLYMER AND MATERIALS CHEMISTRY
TS1 OM1
MATERIALS ANALYSIS AND EVALUATION IN THE SEMICONDUCTOR INDUSTRY
Leonorina G. Cada1,2
1Staff Scientist, Materials Analysis and Evaluation Group, Technology Operations
On Semiconductor, Governor’s Drive, Carmona, Cavite
2Institute of Chemistry, University of the Philippines, Diliman
This paper aims to discuss the role of a chemist in a semiconductor industry such as On Semiconductor. The making of a microchip involves several steps from wafer fabrication to front of line assembly to backend assembly. In all these steps, materials in the form of ceramics, polymers, inorganic and organic formulations are used. Materials analysis and evaluation are conducted to ensure the manufacturability and reliability of the electronic packages that are produced and to complement failure analysis whenever issues arise. A chemist tasked to perform such analysis needs to be familiar with the manufacturing process and the different analytical tools that would enable her to determine composition of materials, presence of bulk and surface contaminants, surface roughness and other materials properties. Equipped with thermal analysers (DSC, TMA, TGA), FTIR-Microscope and AFM, the author wishes to present the different techniques of materials characterization deemed so important in the manufacture of surface mount microelectronic packages. Physical properties like the glass transition temperature and coefficient of thermal expansion that are critical to package integrity are measured using DSC and TMA. In the absence of a better tool, confirmation of composition of raw polymeric materials such as the mold pellets and carrier tapes is done using TGA. Resin bleed, which can lead to a lot of problem in post plating of the metal leadframes, is best detected using an FTIR microscope. Environmental issues like emission of potentially hazardous volatile organic compounds from the molding process can be resolved using TGA. Problems with bonding metal to metal may be traced to surface roughness, a property that can be measured using AFM. Other issues that can be resolved using the above mentioned analytical tools will be presented in this paper.
TS1 OM2
Electrochemical detection of single latex particles
Koichi Aoki
Department of Applied Physics, Fukui University (Japan)
A microscopic image of an electrode reaction is the collision of molecules with the electrode surface, followed by charge transfer and salvation. This is only a series of conceivable steps, and cannot be observed as a time-sequence of individual steps, because each step is averaged. Even if current values are decreased to 1 pA for low concentrations at a microelectrode, a potentiostat cannot follow the time resolution (0.1 m s) required for the detection of an individual event. A possible electrochemical approach to the detection is to simulate a redox species with an artificially enlarged redox particle, e.g. a colloid, which has an extremely large value of the number of Coulombs transferred. This approach corresponds to increasing the ratio of the size of a redox species to the size of the experimental system, as has been made in the study of ionic interactions of monodispersed colloidal particles. Consequently, the microscopic behavior of the redox species is magnified, so that it is observed on a macroscopic scale. Thus, the time scale of particle diffusion is also scaled up appropriately, and hence may fall within the time resolution of an instrument.
This paper is devoted to the analysis of the electrode reaction of a polyaniline-coated polystyrene (PAPS) latex suspension, previously synthesized which works as a redox couple.
TS1 OM3
SYNTHESIS AND CHARACTERIZATION OF POTENTIAL FERROELECTRIC LIQUID CRYSTALS
Larry R. Manuel1, Leonorina G. Cada1 and L. C. Chien2
1Institute of Chemistry, University of the Philippines, Diliman
2Liquid Crystal Institute, Kent State University, Ohio, USA
R- and S- 2-oetyl-4"-decyloxy-2,3’-difluoroterphenylate were synthesized to gain more knowledge on structure-property relationships of ferroelectric liquid crystals. The pertinent structural features in these compounds for ferroclectric formation are the 2,3’ positions of the lateral Fluorines in the ring and the respective donor-acceptor effect of the ethoxy-ester terminal functionalities. These two optically active compounds may be used as dopants. The unsaturated analog, with the terminal vinyl moiety, S-octyl-4"-decenyloxy-2,3’-difluoroterphenylate was synthesized to further enhance the possibility of observing ferroelectric behavior. It may also be attached as the pendant group for the synthesis of a side-chain liquid crystal polymer later on. 1H NMR, 13C NMR and FTIR were employed for structural determination. Reversed phase HPLC (for percentage purity determination), DSC (for determination of transition temperatures), OPM and x-ray (for texture determination) measurements were also done. The variation of spontaneous polarization, Ps, on temperature was determined using the triangular wave method while the dependencies of the response time, t , and the tilt angle, q , on temperature were obtained using square waveforms. These last three aforementioned electrooptic measurements were specifically employed for the vinyl compound. Lastly, the optically active compounds were subjected to polarimetric measurements.
TS2 OM4
MODIFICATION OF THERMORESPONSIVE POLY(N-ISOPROPYLACRYLAMIDE) BY COUPLING WITH CRITOSAN
Clovia Isabel Z. Holdsworth and Rommel G. Patiggo
Chemistry Department, De La Salle University, Taft Avenue, Manila
Temperature-sensitive poly(N-isopropylacrylamide (PiPAAm) exhibits a dramatic solubility change, from soluble to insoluble, at its lower critical solution temperature (LCST) in aqueous solution. When chemically crosslinked to form a gel, substantial discontinuous volume phase transition, from a swollen to a collapsed state, in response to external temperature changes takes place at its lower critical gel transition temperature (LCGTT). It is possible to alter the phase transition behavior of PiPAAm polymers by coupling with other biomlecules. This is usually done to extend its utility in controlling drug delivery rates by temperature change, demonstrating its potential to achieve an intelligent drug delivery system.
We have successfully coupled ester-activated endreactive PiPAAm with chitosan, via its amino groups, by the condensation reaction. Mono- and di-carboxy endgroups of PiPAAm were introduced by free radical chain transfer to mercaptopropionic acid and 3,3-dithiopropionic acid, respectively, and converted to the more reactive ester by reacting with N-hydroxysuccinimide. The effect of the degree of crosslinking between chitosan and PiPAAm on the phase transition behavior of the latter is currently being investigated and will also be presented. Chitosan is a non-toxic and biodegradable polysaccharide and has also been identified as a material for drug delivery systems.
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REPEATED RETENTION AND RELEASE OF LEAD AND CADMIUM IN CARRAGEENAN-POLY(N-ISOPROPYLACRYLAMIDE) SEMI-INTERPENETRATING NETWORKS
Hazel Lym O Tan and Ma. Assunta C. Cuyegkeng
Chemistry Department, Ateneo de Manila University, Loyola Heights, Quezon City
Previous papers by the author have shown the capacity of various carrageenan-poly(N-isopropylacrylamide) (pIPAAm) semi-IPNs to absorb metals like lead, cadmium and zinc. In this series of experiments, the semi-IPN with optimum performance was chosen to test its applicability in scavenging heavy metals from solutions. Upon absorption of the heavy metals, the semi-IPN was subjected to deswelling-swelling experiments that would test if the material could be reused repeatedly.
To facilitate the repeated retention-release cycles, and to see if the semi-IPN could be packaged for the purpose, the carrageenan-pIPAAm hydrogel was contained in a 4cm x 6cm teabag from a tissue-like cellulosic material (Nappy liners). The hydrogels would visibly swell below LCST and collapse when heated to about 40oC. The amount of heavy metals in the various solutions was studied using atomic absorption spectroscopy (AAS). Parallel studies on the differential scanning calorimetry (DSC) further confirmed the LCST of the chosen material.
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MATERIALS AND PROPERTIES OF ENVIRONMENT-FRIENDLY MOLDING COMPOUNDS USED IN ELECTRONIC PACKAGING
Leonorina G. Cada1,2 and R. Lalanto1
1Materials Analysis and Evaluation Group, Technology Operations On Semiconductor, Governor’s Drive, Carmona, Cavite
2Institute of Chemistry, University of the Philippines, Diliman
Global efforts to reduce and eventually eliminate the use of potentially hazardous halogenated compounds have driven research in the semiconductor industry to find suitable alternatives for existing product formulations. At On Semiconductor Philippines Inc., different non-halogenated molding compounds (common name: green molding compounds) were evaluated in terms of thermal stability as compared to existing formulations for microchip encapsulation. The study was conducted parallel to the evaluation of the manufacturability and reliability of different electronic packages based on these green molding compounds. Knowing the thermal stability of the molding compounds can be helpful in optimizing mold process parameters, if needed, and in predicting reliability, when necessary. The data obtained from thermogravimetric analysis (TGA) revealed higher decomposition temperatures for molding compounds containing magnesium hydroxide or phosphorous compounds as flame-retardant relative to the decomposition temperatures for existing halogenated molding compounds. Decomposition temperatures of green molding compounds range from 348-380oC; whereas, for the currently used halogenated formulations, the decomposition temperature range is lower (328-339oC). A preliminary study on the decomposition products of culls and runners, considered as waste products from the molding process, was conducted using TGA coupled with Fourier Transform Infrared (FTIR) spectroscopy. Identified spectra of decomposition products for green molding compounds based on orthocresol novolac resins were predominantly acetone, cresols and phenols. Culls and runners from existing biphenyl-based molding compounds yielded methanol, phenols and acrylic esters upon thermal decomposition. A more thorough study on the decomposition products using GCMS (gas chromatography combined with mass spectroscopy) was also undertaken. This paper discusses the relative thermal stability of the green molding compounds and its potential impact on environmental concerns of the industry and on package robustness.
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CHARACTERIZATION OF COMPATIBLE BLENDS OF k -CARIRAGEENAN AND 4-VINYLPYRIDINE COPOLYMERS
Charo T. Balgua, Clovia Isabel Z. Holdsworth, Victoria dlF. Quirino
Chemistry Department, De La Salle University, Taft Avenue, Manila
We have earlier reported successful synthesis of stable compatible blends of k -carrageenan (k -CARR) and poly(4-vinylpyridine-co-methacrylonitrile) (P4VPyMAN) and poly(4-vinylpyridine- co-vinyl acetate) (P4VPyVA) by allowing both components to interact by acid-base reaction in solution. k -Carrageenan is a linear ionic polysaccharide with sulfate moieties and, under acidic condition, can act as a proton donor due to the accessibility of the hydrogen in the sulfate group. The nitrogen in the pyridine group of 4-vinylpyridine acts as the proton acceptor.
k -CARR/P4VPyMAN and k -CARR/P4VPyVA blends were prepared by (1) varying the copolymer composition (2) varying the k -CARR-vinyl copolymer blending ratio. The morphological features, thermal transitions and thermomechemical behavior of these composite films indicate that their performance is affected by both the blending ratio and copolymer composition. Results of the characterization tests will be presented.
MP1
CONTROLLED RELEASE OF METHYL SALICYLATE IN CHITOSAN-POLY(N-ISOPROPYLACRYLAMIDE) SEMI-INTERPENETRATING NETWORKS
Terence G. Henares and Ma. Assunta C. Cuyegken
Chemistry Department, Ateneo de Manila University, Loyola Heights, Quezon City
A semi-interpenetrating network (semi-IPN) was produced by polymerizing N- isopropylacrylamide (NIPAAm) in the presence of chitosan and cross-linking agent, ethylene glycol dimethacrylate (EGDMA). The resulting material did not swell as much as poly(N-isopropylacrylamide) (pIPAAm), but still showed temperature- and pH- responsiveness. Swelling and DSC experiments showed that the LCST of the material was at 31oC.
The semi-IPN was swollen below 30oC but collapsed at this temperature. This is in the same range as the LCST of carrageenan-pIPAAm semi-IPN. The chitosan-pIPAAm semi-IPN was in a collapsed state and reached maximum swelling at pH 9. Pure pIPAAm and pure chitosan both became swollen at a lower pH.
Methyl salicylate was absorbed by the semi-IPN. Its release was monitored with respect to time and temperature. Results show that the substrate is slowly released with time, indicative of the usual diffusion processes. The temperature-responsive release of methyl salicylate was more pronounced at the LCST of 31oC.
MP2
THERMOPLASTIC STARCH: A Study on the Effect of Fatty Acids from Coconut Oil on its Physico-mechanical Properties
Jerry G. Lanorio1, Marisa Paglicawan2 and Leonorina G. Cada3
1Institute of Chemistry, University of the Philippines, Diliman
2Department of Science and Technology, Bicutan, Taguig, Metro Manila
3On Semiconductor, Governor’s Drive, Carmona, Cavite
Recent studies show that addition of biological additives to thermoplastic starch significantly affects the properties of the biodegradable plastic. This study investigates on the effect of the addition of fatty acids extracted from a locally available coconut oil on the physical and mechanical properties of thermoplastic starch. FT-IR spectroscopy, Differential Scanning Calorimetry, Scanning Electron Microscopy and Tensile Strength Testing were used to characterize the extruded samples. FT-IR spectra showed no significant changes in the functional groups present while DSC measurements indicated an elevation in melting point and heat of fusion. Scanning electron micrographs showed a higher degradation rate for the fatty acid- containing sample, as evidenced by the presence of larger holes. Tensile strength increased with increased screw speeds and heating temperatures in the extrusion but decreased with addition of fatty acid and with water immersion.
MP3
PREDICTING OPTIMUM CURING PARAMETERS OF MOLDING COMPOUNDS USING ISOTHERMAL KINETIC STUDY
Leonorina G. Cada1,2 and R. Lalanto1
1Materials Analysis and Evaluation Group, Technology Operations On Semiconductor, Governor’s Drive, Carmona, Cavite,
2Institute of Chemistry, University of the Philippines, Diliman
The semiconductor industry uses different types of epoxy resins as encapsulants of electronic packages. Mostly in the solid pellet form, the prepolymer resin is melted as they are subjected to heat and pressure inside the mold cavities and is finally cured to a thermoset. The average curing time and temperature are usually set based on the recommendation of the resins supplier. The cured units may or may not undergo post-curing, which would usually take additional hours of heating. This extra step is performed as suggested, again, by the supplier. Reducing curing time and temperature and elimination of post-curing can drastically reduce cost of manufacturing. The resins supplier can suggest a wide range of curing time and temperature, hence, there is a still a need for optimization of the curing parameters. At On Semiconductor Philippines, the tasks of finding the shortest possible cure time and of evaluating feasibility of eliminating the post-curing process were systematically done using differential scanning calorimetry. The mechanism in the curing process involved an externally catalysed epoxy ring-opening reaction between the resin and the hardener. This paper reports the technique used in conducting the needed isothermal kinetic study and the resulting curing parameters for the different types of epoxy resins.
